依赖倒置原则（Dependence Inversion Principle，DIP）：
- 代码设计要依赖于抽象接口，不要依赖于具体实现。
- 通过面向抽象的编程方式来降低类之间的耦合，便于扩展。
反例示例：
class LuckyDrawController { prizeRandom(users: User[], count: number): User[] { ... } prizeWeight(users: User[], count: number): User[] { ... } }
UML类图：
代码实现：
class User { name: string; // 用户名 level: number; // 会员等级 active: number; // 活跃值 constructor(name: string, level: number, active: number) { this.name = name; this.level = level; this.active = active; } }
抽奖接口：传入所有参加抽奖的用户，返回得奖的用户
interface ILuckyDraw { prize(users: User[], count: number): User[]; }
全随机抽奖类
class RandomLuckyDraw implements ILuckyDraw { prize(users: User[], count: number): User[] { // 洗牌 const shuffleUsers = _.shuffle(users); // 随机抽取三位用户 return _.sampleSize(shuffleUsers, count); } }
按权重抽象
class WeightLuckyDraw implements ILuckyDraw { prize(users: User[], count: number): User[] { // 排序 const sortUsers = _.orderBy(users, ["level", "active"], ["desc", "desc"]); // 抽取前三位 return _.take(sortUsers, count); } }
运行示例：
import { RandomLuckyDraw, WeightLuckyDraw, User } from "./DIP"; // 生成随机用户 let users = []; for (let i = 0; i < 10; i++) { const user = new User( Mock.Random.cname(), Mock.Random.integer(0, 10), Mock.Random.integer(50, 100) ); users.push(user); } // 随机抽奖 const randomLuckyDraw = new RandomLuckyDraw(); const winners1 = randomLuckyDraw.prize(users, 3); console.log(winners1); // 权重抽奖 const weightLuckyDraw = new WeightLuckyDraw(); const winners2 = weightLuckyDraw.prize(users, 3); console.log(winners2);
